The goals of the Radiation Biology & Imaging (RBI) Program remain unchanged since the last review of the ACC Core Grant. The RBI program seeks to improve the outcome of patients through the advanced understanding of how ionizing and non-ionizing radiation interacts with cancer and normal tissues. Through the RBI Program, investigators from diverse backgrounds and multiple Departments within the School of Medicine, Veterinary School and the School of Engineering, are brought together to identify the molecular and physiological determinants of radiation and PDT response in tumors. New areas of focus developed in the last two years include the use of nanomaterials to deliver therapeutic and imaging agents to tumors and the use of sophisticated imaging and radiation delivery approaches to better define and evaluate targets and treat tumors with the lowest possible damage to normal tissues. These new efforts have been strengthened with a substantial recruitment effort of new members into the RBI program. The programmatic goals are: 1. to understand the basic molecular mechanisms underlying the cellular response to radiation and to develop molecular targets for manipulating the response of tumors to drugs and ionizing radiation; 2. to develop clinical trials for photodynamic therapy and understand the underlying molecular and physiologic mechanisms that underlie its use; 3. to develop mechanisms to test and validate invasive and non-invasive methods for measuring tumor oxygenation and metabolic status; 4. to study the molecular events in the response to DNA damage by ionizing radiation; and 5. to develop imaging techniques that are related to the delivery and underlying mechanisms of radiation.